SURFACE AREAS AND VOLUMES 231
- It costs Rs 2200 to paint the inner curved surface of a cylindrical vessel 10 m deep. If
the cost of painting is at the rate of Rs 20 per m^2 , find
(i) inner curved surface area of the vessel,
(ii) radius of the base,
(iii) capacity of the vessel. - The capacity of a closed cylindrical vessel of height 1 m is 15.4 litres. How many
square metres of metal sheet would be needed to make it? - A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in
the interior. The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm.
If the length of the pencil is 14 cm, find the volume of the wood and that of the
graphite. - A patient in a hospital is given soup daily in a cylindrical bowl of diameter 7 cm. If the
bowl is filled with soup to a height of 4 cm, how much soup the hospital has to prepare
daily to serve 250 patients?
13.8 Volume of a Right Circular Cone
In Fig 13.28, can you see that there is a right circular
cylinder and a right circular cone of the same base
radius and the same height?
Activity : Try to make a hollow cylinder and a hollow cone like this with the same
base radius and the same height (see Fig. 13.28). Then, we can try out an experiment
that will help us, to see practically what the volume of a right circular cone would be!
Fig. 13.29Fig. 13.28